Slow processing?

Ok, so, using the internal pull downs, is it possible to make it so that COMPLETING the circut, rather than detaching it, will turn on the LED? Obviously then setting the ledpin to do what the digitalread on the input pin is doesn't work to do that. I've tried things like this, but nothing has worked so far:

int ledpin=13;
int input=7;
int var2=2;
int scan=0;

void setup()
{
pinMode(ledpin,OUTPUT);
scan=digitalRead(input);
digitalWrite(input,HIGH);
}
void loop()
{
if(scan==HIGH)
{
digitalWrite(ledpin,LOW);
}
else
{
digitalWrite(ledpin,HIGH);
}
}